In the manufacturing industry today, many manufacturers utilize conveyor systems for easily and quickly moving products through various stages of the manufacturing process. For example, in the furniture industry, a piece of furniture may be placed on a conveyor cart connected to a conveyor system which passes through sanding stations, paint booths, finishing stations, hardware stations, etc. Existing conveyor systems typically consist of a series of conveyor carts upon which various items may be placed, a drive chain housing secured to the floor of the manufacturing facility through which a drive chain passes which pulls the conveyor carts, and a drive mechanism for providing locomotion to the chain and thereby moving the conveyor carts.
Examples of known conveying systems are set forth in a number of U.S. patents including U.S. Pat. Nos. 4,438,702; 4,638,740; 4,644,869; 4,770,285; 4,944,228; 4,947,978; 5,065,678; 5,299,680; 5,368,152; 5,538,126; 5,549,050, which Applicant hereby incorporates by reference in their entirety. In these conveyor systems, the load carrying units are provided with vertically movable pins for engaging and disengaging with movable endless chains which move at a constant and continuous speed. Many different means have been used for moving these vertical pins from an engaging to a disengaging position and problems have been encountered in maintaining these pins in a disengaged position as the endless chain continues to move beneath the pins. U.S. Pat. Nos. 4,944,228; 5,368,152; 5,538,126; and 5,549,050, which Applicant hereby incorporates by reference in their entirety, teach various means for stabilizing the engaging pins in a disengaged position.
Other embodiments of these conveying systems include overhead conveyers for propelling a carrier moveably along a track by an endless conveyor chain disposed within the track. The carrier is detachably connected to the chain and includes an uncoupling assembly for detaching the carrier from the chain. U.S. Pat. Nos. 6,378,440; 6,827,200; and 6,843,358, which Applicant hereby incorporates by reference in their entirety, relate to various overhead conveyers.
In typical conveying system configurations, the drive mechanism of current conveyor systems must be placed below the level of the drive chain (i.e., below the surface of the floor). To do this, a large cavity must be created in the manufacturing room floor directly adjacent to and beneath the drive chain housing and drive chain. This cavity houses the drive mechanism. Such a configuration is required in current conveyor systems because as the system operates, the drive chain wears and settles, thus creating excess chain or “slack” in the drive chain. By placing the drive mechanism below the drive chain housing (i.e., below the surface of the floor), excess chain may be collected in the cavity. Normally, the excess chain has a tendency to bind up and become tangled; however, allowing the chain to collect in the cavity allows gravity to act on the excess chain and provide the tension necessary to prevent the excess chain from binding up or tangling. That is, the excess chain exiting the drive mechanism simply hangs freely until pulled up into the drive chain housing.
One problem with mounting the drive mechanism below the drive chain housing in a large floor cavity is that creating the sub-surface cavity is difficult, fixed and expensive. The cavity may be several feet across in width and may extend several feet into the floor beneath the drive chain housing. As most manufacturing facility floors are made of concrete or other similar material, creating such a large cavity in this type of material is both laborious and expensive. Further, the placement of the cavity may be dictated by the specific design of the manufacturing facility floor. For instance, sub-surface pipes, electrical wiring, or other objects may prevent the cavity from being located in certain otherwise desirable locations. As a result, a manufacturing line may need to be re-designed or otherwise modified to account for the placement of the drive mechanism and its cavity, adding yet additional costs and delaying installation of the conveyor system.
An additional issue with existing drive systems is that they may “lose center.” A system loses center when the tow pin for a cart on the chain drive system drifts one or more links from its original starting chain link when moving through the drive portion of a conveyor system. Methods including using “pushers” or other mechanical means to keep a cart “on center” do not completely correct for the problem.
Keeping center is critical for timing sensitive operations such as automotive assembly. In such operations, the exact distance between carts on the conveyor system must be kept at all times to ensure that carts spend the correct amount of time at any given assembly station or point on the conveyor system. If center is not kept, the carts may drift apart or together, and may not arrive at assembly stations at the correct time, or may spend too little or too much time at any given point on the conveyor system.
What is needed is a solution to address the various problems associated with current conveyor systems, including the sub-surface drive mechanism of current conveyor systems and further including the tendency of current drive systems to “lose center” when in operation.